Mannans have been isolated from cells of the following Candida species: C. albicans (serotype A), C. albicans (serotype B), C. parapsilosis, C. stellatoidea, and C. tropicalis. Methylation and hydrolysis of each mannan yielded the following methyl ethers of d-mannose (with only small variations in the relative amounts): 2,3,4,6-tetra-O-methyl-d-mannose, 3,4,6-tri-O-methyl-d-mannose (major), 2,3,4-tri-O-methyl-d-mannose (minor), 2,4,6-tri-O-methyl-d-mannose (minor), 3,4-di-O-methyl-d-mannose, and 3,5-di-O-methyl-d-mannose. The mannans therefore contained a predominance of 1 → 2 linkages in the linear portions, with smaller amounts of 1 → 6 and 1 → 3 linkages. Branching occurred through C-2 and C-6 of d-mannopyranose and d-mannofuranose units, and branches were terminated by d-mannopyranose units. The specific rotations of the mannans indicated that most of the glycosidic linkages were in the α configuration. The structural studies support the observation that the mannans are very similar serologically and show cross-reactivity in antisera to any of the parent organisms.

A two-stage extraction of isolated cell walls of C. albicans resulted in 45% solubilization into antigens of high molecular weight leaving a wall residue which also had antigenic properties. Ice-cold dilute alkali removed 25% of the defatted cell walls. The extract was nondialyzable, had a glucose-to-mannose ratio of 2:3 and an amino acid content of 7.32%, and was designated peptidoglucomannan (PGM). An additional 26% of the walls resistant to stage I were solubilized by sonic treatment yielding a fraction having a glucose-to-mannose ratio of 6:1, termed soluble mannoglucan (sMG). The residue after extraction and sonic treatment contained 10.9% mannose, which was the insoluble mannoglucan. The gel permeation behavior of PGM and sMG on BioGel A5M was similar; each contained two components, one estimated to exceed 5 × 10 6 molecular weight and a second smaller species. The soluble cell wall fractions were active in immunodiffusion and carried antigenic group specificity. Immunoelectrophoresis of PGM, sMG, and mannan revealed some heterogeneity. The insoluble mannoglucan had agglutinating activity. A distinctive immunodiffusion pattern of cell wall antigens was formed with the serum of a leukemic patient with candidiasis. All three cell wall antigens and mannan elicited delayed-type hypersensitivity as measured by skin-test and specific inhibition of macrophage migration. A dose of 25 μg of PGM was sufficient to inhibit 89.9% migration in the peritoneal exudates of guinea pigs immunized with cell walls, and 10 μg of PGM inhibited 91.7% migration in guinea pigs immunized with insoluble mannoglucan.

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